Processes using photosensitive resin compositions are widely used as processes for forming electronic circuits and the like.
In a circuit formation process using a photosensitive resin composition, an electronic circuit is formed by conducting a step of forming a resist film composed of the photosensitive resin composition on the surface of a substrate, a step of forming a latent image by irradiating the resist film with light through a mask, a step of forming a resist pattern by subjecting the resist film with the latent image formed thereon to a developing treatment with a developing solution, and a step of chemically etching or plating the portions from which the resist has been removed.
Further, miniaturization of electronic circuits is being investigated in the fields of chip-on-film (COF) in which a bare chip is mounted directly on a flexible substrate, multilayer printed circuit boards formed by the build-up method, and lead-out wiring which is used in touch panel sensor circuits and tablet terminals and the like. Negative dry film resists have been widely used in circuit formation processes, but many technical problems exist in terms of meeting the current demands for further miniaturization.
On the other hand, positive photosensitive resin compositions are suitable for miniaturization, and hold much hope as materials capable of meeting ongoing demands for miniaturization. However, they lack flexibility and suffer from many problems during circuit formation on flexible substrates and dry film formation.
Examples of currently known positive photosensitive resin compositions include the compositions described below.
(1) A photosensitive resin composition containing a vinyl-based polymer (I) obtained by polymerizing a monomer mixture containing a vinyl-based monomer having a phenolic hydroxyl group, a vinyl-based polymer (II) obtained by polymerizing a monomer mixture containing a carboxyl group-containing vinyl-based monomer, a quinonediazide compound, and an aromatic polyhydroxy compound (see Patent Document 1).
(2) A positive photosensitive composition containing an o-quinonediazide compound, an alkali-soluble resin, and a specific bisphenol carboxylic acid derivative (see Patent Document 2).
However, in the photosensitive resin composition of (1), the vinyl-based polymer (I) is rigid and lacks flexibility, and also exhibits poor solubility in developing solutions, and therefore when the photosensitive resin composition of (1) is used as a resist film, the combination of cracking resistance and resolution for the resist film is not entirely satisfactory. When the photosensitive resin composition of (1) is converted to a dry film, because the dry film is wound, the above problems become particularly obvious.
In the positive photosensitive composition of (2), the alkali-soluble resin is rigid and lacks flexibility, and also exhibits poor solubility in developing solutions, and therefore when the photosensitive resin composition of (2) is used as a resist film, the combination of cracking resistance and resolution for the resist film is not entirely satisfactory. Further, Patent Document 2 makes no mention of the formation of dry films.